That West Side Story is a five-star classic musical is apparent from the hairs that stand up on the back of the neck the moment the band strike up Leonard Bernstein’s stirring score – the opening bars whisk you straight to the bitter heart of New York’s 1950s gangland.

Then you see Paul Gallis’s brilliant set, a maze of ladders and balconies evoking tenement blocks backdropped by giant skyscrapers, and everything about this 50th anniversary production of the masterwork by Jerome Robbins looks set to shine.

But though the hits just keep on coming, the fireworks somehow fizzle in mid-flight. The clue lies in the credits. Director Joey McKneely, under strict guidelines from the Jerome Robbins estate, which insists that the original dance is not tampered with, is listed in the programme under ‘choreography reproduced by’. Fair enough, there’s no doubt that the Robbins original is a benchmark by which musicals should be judged. But here it feels like a hand-me-down, the edge lost by too much reverence.

The street-sharp encounters between the Jets and the Sharks, which should form the electric heart of West Side Story, never take off – a finger-click short of the full snap, crackle and pop. Though the theme of alienated children in urban gangs torn apart by knife crime carries a sharp contemporary relevance, this West Side Story remains marooned in its own time.

Yet for all that, there is plenty to enjoy. You can’t go far wrong with tunes such as Tonight, Maria and I Feel Pretty, and Ryan Silverman and Sofia Escobar sing up a storm as Tony and Maria, the Romeo and Juliet substitutes in West Side Story’s Shakespearean twist. They make for believable young lovers, self-absorbed and starry-eyed.

Even the throwaway songs would make it as showstoppers in any other musical but there are moments when West Side Story shows its age. America, the wide-eyed celebration of Uncle Sam sung by Puerto Rican girls, these days needs a shot of irony to make it work. And Somewhere, the show’s signature tune, is diluted by a dated dream sequence Robbins must have done in his sleep.

At the end of the show, you can’t help but come out humming the tunes. But West Side Story deserves more than to be turned into a museum piece.